I need some help guys. I’m building DRV8825-HW203 FULL OLED and using Code Arduino DRV8825_HW203_F_OLED. Everything is still on a breadboard and I’m testing. I’ve ran into few problems so far.
When I use the IN and OUT push buttons, Blue and Green LEDs barley lit up. Measuring the voltage at A1 and A2 on Arduino gives me only 0.002V. Now, if I reset the controller and measure voltage at the same time, I briefly get 4.7V, but that’s about it. All of the above is also true for pin A3 as well.
I’m using NEMA17 stepper motor. DRV8825 current was set to 290mA as per the PDF. If I have Stepper Coil Power turned ON, then 10-15min later my motor gets hot, and I mean it’s really hot. Micro stepping is set to Full (like I said, I’m still bench testing).
And the last one. Micro stepping is set to Full and I test stepper motor through Win app, it runs smooth as butter. Now, If I enable “LCD/TFT during move”, the motor begins to jerk during spinning. If I disable “LCD/TFT During move”, everything works just fine, so I’m not sure what is going on there.
Hi Lubo
1. LEDs - No issue, that is correct. the pulse to step the motor is very short, so measuring it with a multimeter you will not see it. It is working as expected. It is better to use the test programs in https://sourceforge.net/projects/arduinoascomfocuserpro2diy/files/Testing/ for testing purposes. They will give better indications. But as I said, what you see is normal. The LEDS will give a brief pulse.The buzzer is enabled on reset/power up only for a brief beep.
Yes, again this issue is mentioned in the pdf and the faq (page6). Enabling the LCD/TFT during a move gives a real update of position during the move - which means the controller has to stop what it is doing (moving), send the value for position and then resume moving. So yes there will be a pause.
In normal operation your moves in focusing are going to be very small, in the order of 100 or less steps, not a 1000. It does not make sense to have LCD update during move on because the distance is so small and small moves happens quick.
The Arduino is not a proper multitasking computer. If moves were made non-blocking (in other words tell it to complete the move before doing anything else) then the controller would be unresponsive till the move is completed, meaning that any command request such as halt etc would be ignored and the application would time out.
Within the arduino firmware file there is a line
int lcdupdatestepcount = 15; // the number of steps moved which triggers an lcd update when moving
This line says that during a move, if LCD update when moving is enabled, the lcd will update on every 15 focus positions. You can change this to 20, 50 or even100 if you want to reduce the number of interruptions.
So please have some assurance that your build is working as expected.
You did not say what NEMA stepper model model number you are using. The 17HS13-0404S-PG5?
If you measured the current flowing in the stepper coils, there is no harm in reducing the current a bit more.If you are using full steps then you can turn coil power off. If you need to use microstepping on the telescope to get the right number of steps within the CFZ then you have no option but to use coil power on to hold the stepper motor at the correct position.
Heat is a function of current and voltage. Doing the math, 12V and 260mA gives 3 watts of power (6 watts taking into account two coils) which is minimal to say the least. I would recheck what voltage and current you are getting on the stepper coils.
The 12V lead acid battery is probably putting out around 13.5V fully charged, so that extra 1.2V per coil means more heat. There is no regulation on the power going to the DRV8825 Vmot pin, so that means more voltage across the stepper motor thus more heat. So reduce current accordingly
Alternative see note 2 page 31 of PDF and adjust stepper current manually. This often gives good resuts and a cooler motor. I have not measured my own current but I use the manual method for all my focuser builds and they do not seem to run hot even after 10-20m.
Let me know how it goes, if I havent answered some questions, please let me know, am only too happy to chat
Cheers
Robert
Last edit: brownrb 2016-12-30
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Thank you Robert. I followed your advice and adjusted stepper current manually. It’s really easy, you hear/feel the motor stutter, then runs kinda smooth with high pitching sound and 1/8 of a turn later it’s just butter smooth with no pitching sound and done. I personally like voltage/current because it’s more precise but I guess in the ballpark works as well.
I’m using just a regular NEMA 17 - 17HS13-0404S and might go with belt and reduction gears later, I haven’t decided yet.
To address the external power supply, the battery is not fully charged and it outputs 11.8V and about 10.8V after 10A02 diode I use. So, DRV8825 doesn’t get that much.
Did a quick experiment, measured current separately on each coil of the stepper while adjusting the pot, DRV8825 would not exceed 290mA on each coil, no matter what. Even though the voltage was from 0.0 to 3.2. The other thing I didn’t like about this driver is continuous spinning pot whilst Easydriver has end-to-end.
On the other hand, LCD issue is pretty clear cut and thank you for pointing the FAQ. I guess I won’t be using LCD update while moving.
If I disable coil power then motor shaft is moving freely, so I don’t know how it would hold the focuser and imaging gear. During my testing stepper got really hot (CP was On), now that I can measure the temperature using the probe, it got to 45 Celsius and climbing, it’s where I shut it down. Here is a pic:
EDIT: Couldn't upload the pic, it shows temp probe attached to stepper at 45 Celsius.
Btw, I’m still convinced there’s something going on with LEDs. I haven’t added resistors yet and there are dim, I made a short video: https://www.youtube.com/watch?v=xMcN8sTfPPE
I might have to start from scratch just to see if I connected everything as it supposed be instead of tracing all cables and all else. One thing that really bothers me is the stepper overheating tho.
Again, thanks for your help Robert
Last edit: Lubo Lichkov 2016-12-30
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LEDS look ok in the video. As expected. They are pulsed at 2us per step when moving, as the DRV8825 needs a step pulse of 2us to step.
On reset, the LEDS are turned on at start of setup() and turned off at end of setup() - hence are on for longer hence will be brighter.
Think of the LEDS being pulsed at the same rate as the stepper when moving - hence on for 2us, off for some time, on for 2us etc - hence they will be dimmer.
You could change
int stepontime = 2; // DO NOT CHANGE
to 10 but not any higher. You may then need to readjust the speed values to compensate.
I also have the 404S on all my scopes, a PG5 and PG27 and a standard one. I have about 250mA flowing and I run with Coil Power on and half steps. If I didnt my heaving imaging train would just play havoc. I do not suffer the heat issues at all. Steppers are only slightly warm even after an hour of so of imaging.
So I suspect an issue with the DRV8825 (u could drop in a replacement EasyDriver with minimal change). I believe the DRV is a chopper so it may be faulty. I see the capacitor on the DRV breadboard.
I do know there has been previous reported heat issues with stepper motor - those were resolved by adjusted current and in another case by replacing drv chip.
The 404S has a phase resistance of 30 ohms. So with10.8V across it maximum current would be 360mA per phase. I would certainly try another DRV chip.
Please update me on progress I am interested to see how things go.
Cheers
Robert
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Hi Lubo
I have a new beta version for the OLED if you wish to test it.
This will form the basis for next major release.
I have rewritten code based on timer interrupts.
What this means for you is
1.the lcd update during move works without any slowdown or jerk on the stepper motor
2.All stepper speeds are now controlled by a timer, means consistent speeds across different driver boards as well as users, we should all end up with the same speeds regardless of the hardware.
3.Advice is to NOT change any code in this firmware release as there are a lot of interdependencies
If you want to try it out please email at yahoo, brown_rb and I will email you the code. Only conditions are report back issues and please do not forward the beta code to anyone else.
Regards
Robert
For other users with a DRV8825_HW203_F board, if you wish to try the next beta release let me know.
I also have the ULN2003_F beta code.
Other beta versions are not available at this time.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello Robert,
is this beta code part of 270? I'm running into pretty heavy stuttering when activating the OLED update on move. I actually though I had burned a board, I desoldered and replaced my driver, replaced the arduino all to later see that all stutters were synced with oled updates or serial polls from the windows app.
Great awesome focuser BTW, thanks for sharing I had a blast building it!
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi Michel
We have just released 271. As all graphic options involve libraries written by other parties, we cannot control what those libraries do or whether they block calls etc.
We do recommend that display updating when moving be disabled. The arduino is a lightweight chip that really is not designed to run fast or multi-task. This means when its doing something like moving the motor and you also want to update the display something has to give. It has to stop moving the motor when updating the display. Hence stutter. But it should notbe too excessive
If you can post a video of the stuttering that would help
Regards
Robert
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I need some help guys. I’m building DRV8825-HW203 FULL OLED and using Code Arduino DRV8825_HW203_F_OLED. Everything is still on a breadboard and I’m testing. I’ve ran into few problems so far.
When I use the IN and OUT push buttons, Blue and Green LEDs barley lit up. Measuring the voltage at A1 and A2 on Arduino gives me only 0.002V. Now, if I reset the controller and measure voltage at the same time, I briefly get 4.7V, but that’s about it. All of the above is also true for pin A3 as well.
I’m using NEMA17 stepper motor. DRV8825 current was set to 290mA as per the PDF. If I have Stepper Coil Power turned ON, then 10-15min later my motor gets hot, and I mean it’s really hot. Micro stepping is set to Full (like I said, I’m still bench testing).
And the last one. Micro stepping is set to Full and I test stepper motor through Win app, it runs smooth as butter. Now, If I enable “LCD/TFT during move”, the motor begins to jerk during spinning. If I disable “LCD/TFT During move”, everything works just fine, so I’m not sure what is going on there.
My external power supply is sealed lead acid 12V 7.2Ah battery similar to this:
https://www.amazon.com/dp/B01I0VNV1U?psc=1
Thank you and any help is appreciated.
Hi Lubo
1. LEDs - No issue, that is correct. the pulse to step the motor is very short, so measuring it with a multimeter you will not see it. It is working as expected. It is better to use the test programs in https://sourceforge.net/projects/arduinoascomfocuserpro2diy/files/Testing/ for testing purposes. They will give better indications. But as I said, what you see is normal. The LEDS will give a brief pulse.The buzzer is enabled on reset/power up only for a brief beep.
In normal operation your moves in focusing are going to be very small, in the order of 100 or less steps, not a 1000. It does not make sense to have LCD update during move on because the distance is so small and small moves happens quick.
The Arduino is not a proper multitasking computer. If moves were made non-blocking (in other words tell it to complete the move before doing anything else) then the controller would be unresponsive till the move is completed, meaning that any command request such as halt etc would be ignored and the application would time out.
Within the arduino firmware file there is a line
int lcdupdatestepcount = 15; // the number of steps moved which triggers an lcd update when moving
This line says that during a move, if LCD update when moving is enabled, the lcd will update on every 15 focus positions. You can change this to 20, 50 or even100 if you want to reduce the number of interruptions.
So please have some assurance that your build is working as expected.
You did not say what NEMA stepper model model number you are using. The 17HS13-0404S-PG5?
If you measured the current flowing in the stepper coils, there is no harm in reducing the current a bit more.If you are using full steps then you can turn coil power off. If you need to use microstepping on the telescope to get the right number of steps within the CFZ then you have no option but to use coil power on to hold the stepper motor at the correct position.
Heat is a function of current and voltage. Doing the math, 12V and 260mA gives 3 watts of power (6 watts taking into account two coils) which is minimal to say the least. I would recheck what voltage and current you are getting on the stepper coils.
The 12V lead acid battery is probably putting out around 13.5V fully charged, so that extra 1.2V per coil means more heat. There is no regulation on the power going to the DRV8825 Vmot pin, so that means more voltage across the stepper motor thus more heat. So reduce current accordingly
Alternative see note 2 page 31 of PDF and adjust stepper current manually. This often gives good resuts and a cooler motor. I have not measured my own current but I use the manual method for all my focuser builds and they do not seem to run hot even after 10-20m.
Let me know how it goes, if I havent answered some questions, please let me know, am only too happy to chat
Cheers
Robert
Last edit: brownrb 2016-12-30
Thank you Robert. I followed your advice and adjusted stepper current manually. It’s really easy, you hear/feel the motor stutter, then runs kinda smooth with high pitching sound and 1/8 of a turn later it’s just butter smooth with no pitching sound and done. I personally like voltage/current because it’s more precise but I guess in the ballpark works as well.
I’m using just a regular NEMA 17 - 17HS13-0404S and might go with belt and reduction gears later, I haven’t decided yet.
To address the external power supply, the battery is not fully charged and it outputs 11.8V and about 10.8V after 10A02 diode I use. So, DRV8825 doesn’t get that much.
Did a quick experiment, measured current separately on each coil of the stepper while adjusting the pot, DRV8825 would not exceed 290mA on each coil, no matter what. Even though the voltage was from 0.0 to 3.2. The other thing I didn’t like about this driver is continuous spinning pot whilst Easydriver has end-to-end.
On the other hand, LCD issue is pretty clear cut and thank you for pointing the FAQ. I guess I won’t be using LCD update while moving.
If I disable coil power then motor shaft is moving freely, so I don’t know how it would hold the focuser and imaging gear. During my testing stepper got really hot (CP was On), now that I can measure the temperature using the probe, it got to 45 Celsius and climbing, it’s where I shut it down. Here is a pic:
EDIT: Couldn't upload the pic, it shows temp probe attached to stepper at 45 Celsius.
Btw, I’m still convinced there’s something going on with LEDs. I haven’t added resistors yet and there are dim, I made a short video:
https://www.youtube.com/watch?v=xMcN8sTfPPE
I might have to start from scratch just to see if I connected everything as it supposed be instead of tracing all cables and all else. One thing that really bothers me is the stepper overheating tho.
Again, thanks for your help Robert
Last edit: Lubo Lichkov 2016-12-30
LEDS look ok in the video. As expected. They are pulsed at 2us per step when moving, as the DRV8825 needs a step pulse of 2us to step.
On reset, the LEDS are turned on at start of setup() and turned off at end of setup() - hence are on for longer hence will be brighter.
Think of the LEDS being pulsed at the same rate as the stepper when moving - hence on for 2us, off for some time, on for 2us etc - hence they will be dimmer.
You could change
int stepontime = 2; // DO NOT CHANGE
to 10 but not any higher. You may then need to readjust the speed values to compensate.
I also have the 404S on all my scopes, a PG5 and PG27 and a standard one. I have about 250mA flowing and I run with Coil Power on and half steps. If I didnt my heaving imaging train would just play havoc. I do not suffer the heat issues at all. Steppers are only slightly warm even after an hour of so of imaging.
So I suspect an issue with the DRV8825 (u could drop in a replacement EasyDriver with minimal change). I believe the DRV is a chopper so it may be faulty. I see the capacitor on the DRV breadboard.
I do know there has been previous reported heat issues with stepper motor - those were resolved by adjusted current and in another case by replacing drv chip.
The 404S has a phase resistance of 30 ohms. So with10.8V across it maximum current would be 360mA per phase. I would certainly try another DRV chip.
Please update me on progress I am interested to see how things go.
Cheers
Robert
Hi Lubo
I have a new beta version for the OLED if you wish to test it.
This will form the basis for next major release.
I have rewritten code based on timer interrupts.
What this means for you is
1.the lcd update during move works without any slowdown or jerk on the stepper motor
2.All stepper speeds are now controlled by a timer, means consistent speeds across different driver boards as well as users, we should all end up with the same speeds regardless of the hardware.
3.Advice is to NOT change any code in this firmware release as there are a lot of interdependencies
If you want to try it out please email at yahoo, brown_rb and I will email you the code. Only conditions are report back issues and please do not forward the beta code to anyone else.
Regards
Robert
For other users with a DRV8825_HW203_F board, if you wish to try the next beta release let me know.
I also have the ULN2003_F beta code.
Other beta versions are not available at this time.
Hello Robert,
is this beta code part of 270? I'm running into pretty heavy stuttering when activating the OLED update on move. I actually though I had burned a board, I desoldered and replaced my driver, replaced the arduino all to later see that all stutters were synced with oled updates or serial polls from the windows app.
Great awesome focuser BTW, thanks for sharing I had a blast building it!
Hi Michel
We have just released 271. As all graphic options involve libraries written by other parties, we cannot control what those libraries do or whether they block calls etc.
We do recommend that display updating when moving be disabled. The arduino is a lightweight chip that really is not designed to run fast or multi-task. This means when its doing something like moving the motor and you also want to update the display something has to give. It has to stop moving the motor when updating the display. Hence stutter. But it should notbe too excessive
If you can post a video of the stuttering that would help
Regards
Robert
Hi@all,
the "poor" LED brightness on the move, i put a Monostable Multivibrator on the output, so i have a longer puls as 2us for the LED.
Regards
Andreas
Hi Andreas
Good thinking, I am sure may will find this very helpful.
Cheers
Robert